(a) Technical Field
The present disclosure relates to a light source for a display device.
(b) Discussion of the Related Art
Display devices used for image display such as in a television receiver or computer monitor are classified into a self-luminescence display and a light-receiving display requiring a separate light source. Light emitting diode (LED), electroluminescence (EL), vacuum fluorescent display (VFD), field emission display (FED), and plasma display panel (PDP) devices, etc., are included in the self-luminescence display device, while liquid crystal displays (LCDs), etc., are included in the light-receiving display devices.
The LCD includes, for example, a pair of panels individually having electrodes on their inner surfaces, and a dielectric anisotropy liquid crystal layer interposed between the panels. In the LCD, a variation of the voltage difference between the field generating electrodes, i.e., the variation in the strength of an electric field generated by the electrodes, changes the transmittance of the light passing through the LCD, and thus desired images are obtained by controlling the voltage difference between the electrodes.
In the LCD, a light may be a natural light or an artificial light emitted from a light source unit separately employed in the LCD.
A backlight device is a representative artificial light source device for the LCD. The backlight device utilizes light emitting diodes (LEDs) or fluorescent lamps such as cold cathode fluorescent lamps (CCFLs), external electrode fluorescent lamps (EEFLs), etc., as the light source.
The LED is eco-friendly since it does not use mercury (Hg) and it has stable characteristics. For these reasons, the LED is a preferred light source.
However, some problems may arise when the LED is used as a surface light source device. This is because the light rays emitted from the LED tend to condense to a narrow region.